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How can an existing annotated tag be renamed in Git?

I have almost a hundred tags representing version numbers on a repository, and each tag is annotated with a useful description about what was changed that version. I'd like to change the naming style I've used for these tags, and recording the tag message, deleting the tag, and recreating it with the old message and a new name would be a nightmare to do manually for almost a hundred tags. A script or a series of git commands to do this would be useful for automation.

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2 Answers 2

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The bad news is that the name of an annotated tag object is embedded inside that annotated tag object. So if you want to be totally thorough, you'll need to replace those tag objects:

  • If they're signed tags you will need to regenerate them with new signatures.

  • Otherwise, it's possible to copy the tag objects to new tag objects, with the systematic name changes you'd like to make. The filter-branch command does this, for instance. (It's a bit ugly since you have to use some low level plumbing commands; there's no easy convenient method. But see below.)

The good news is that there's no absolute requirement that you use the "correct" annotated tag along with a lightweight tag. That is, an annotated tag is actually a pair of entities: a lightweight tag (with some name that's simply an entry in the refs/tags/ name-space), along with an annotated tag object (in the repository itself) that normally has the same name in its tag field. But you can make a new lightweight tag that points to the existing annotated tag object, then optionally delete the original lightweight tag:

$ git cat-file -p v2.5.0 | sed 's/@/ /' object a17c56c056d5fea0843b429132904c429a900229 type commit tag v2.5.0 tagger Junio C Hamano <gitster pobox.com> 1438025401 -0700 Git 2.5 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAABAgAGBQJVtoa5AAoJELC16IaWr+bLRtQP/0RYjVe9fLubiN5vLaAJ98B5 K3apw8bScJ4bZQJiOGMZg7AJ8pSB9XchqopjNlO2v8XVrZEkFPQ7ln3ELjOITusO 0MIZz6Y4sS0yqMklNPWx/OIzvSyKOs8quUA/J87Ha+pnMYlobDgWJxDnZ3hVO6q2 0lVMRUvwM9qsBiPsVKyAba5qPDBn9uTjgR/hivA3Ha97foq/qMM6rjERp5hX8KTE JacLMlx7ZSAJiNKmz1mVk+xyDVGDh9nojiz93jRYohAM8gsbyyRayPGKlKsMrajC s0bLxilV8zupNrMOs54ND71VqNo992ewiCrB3FBpTah2rPE0MKsxCY72pFiZp/hn w1I3seQbd880d2TXfczVVphG3xN3xbfnC+aEqobgPuFIgGxHqeWqUpDQnWa0XhtK i5phhENEjbMdCDGf7ylRRvCTL5O2Mz1XnNfZBP0uqIX6PyzaCwcZM1DUP0xY8Nvz xo0BplMvK4sAr+fCW0HHHlDO6Ky3jjRyPUEyVEbwF50lZ3Sgzkkf32I06yeZgQW9 Ge6+qGopw7JVQM95UDMBysbQSNuTmwnclwn0DBfc85vQwZw5OwnRk0RsQxcnqNr2 B4Nyubl8Pge4H0T0pahpAdr0AU7JHv4i4yYZh1Dr4d+hzzXAK+ospCxkcJVX7Qz5 BP8pbLPj3ubLAenxg71I =xfTv -----END PGP SIGNATURE----- $ git rev-parse v2.5.0 8d1720157c660d9e0f96d2c5178db3bc8c950436 $ git tag silly v2.5.0 $ git rev-parse silly 8d1720157c660d9e0f96d2c5178db3bc8c950436 $ git tag -d v2.5.0 Deleted tag 'v2.5.0' (was 8d17201) $ git for-each-ref refs/tags/silly 8d1720157c660d9e0f96d2c5178db3bc8c950436 tag refs/tags/silly

(I restored the old tag and deleted the "silly" version after this, so it's not terribly thoroughly tested, but it didn't blow up at least.)

To automate either copying the tags, or re-creating the tags (with or without signatures), simply use git for-each-ref to find all the old tags, and use the resulting names to make the new tags. Use git cat-file -p to pretty-print the existing tag for modifying to make the new tag, or simply make the new tag pointing to the existing tag object. After printing the tag (to a pipe or file) you can edit it with sed or some other programmable editor, and feed the result to git tag -F as an input file, or to git mktag to create a tag object, feeding the resulting SHA-1 to git tag to make the corresponding lightweight tag.

(Note: if you've gotten partway through writing a bash script to do all this, and just need help to finish it up or correct some issue(s) with it, post the script-so-far.)

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1 Comment

I haven't tried it, but your method looks like it'd be quicker to set up than a script. I'll post the script I made which just extracts the useful information from git tag -n99 if I think it could be of use to someone, otherwise thanks for the git-way of doing it =)
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Summarizing torek's answer for the case when you want to rename a single annotated tag v1.0.0 to just 1.0.0

Variant 1: Rename Replace both, lightweight tag and underlying tag object

Warnings:

  • This will break signatures of signed tags. Only use on unsigned annotated tags.
  • A naive sed replacement like below will also change occurrences of v1.0.0 in the tag message and in the tag's tagger name (if any). Use a more specific RegEx if that is not what you intend.
git tag "1.0.0" $(git cat-file -p "v1.0.0" | sed 's/v1\.0\.0/1.0.0/g' | git mktag) # You might want to check the result before continuing to delete the old tag. # Delete the old tag locally git tag -d v1.0.0 # Delete the old tag on the default remote (origin) git push origin :v1.0.0

Variant 2: Rename Replace the lightweight tag only and have it point to the original underlying tag object

git tag "1.0.0" "v1.0.0" # Delete the old tag locally git tag -d v1.0.0 # Delete the old tag on the default remote (origin) git push origin :v1.0.0
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2 Comments

Or you could just not append the "g" tag to your sed command; thus only the first match (which will be the tag name) will be changed.
Or just match the exact format of the line with s/^tag v1\.0\.0$/tag 1.0.0/

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